President Barack Obama says the U.S. is looking at Egypt's escalating political unrest with concern, as opponents of President Mohamed Morsi call for his departure.

During a joint news conference in Pretoria Saturday with South Africa's President Jacob Zuma, Mr. Obama said the U.S. supports peaceful methods to bring about change in Egypt.

"I think every party has to denounce violence. We'd like to see the opposition and President Morsi engaged in a more constructive conversation around how they move their country forward because nobody is benefiting from the current stalemate that exists there."

In Egypt, at least seven people have been killed and hundreds more wounded during days of street fighting between government supporters and opponents.

Authorities say three people were killed Friday, including Andrew Pochter, a young American student who was stabbed to death while photographing protests in Alexandria.

In a statement, Pochter's family said he loved the region's culture and had a summer job teaching English to school children in Alexandria.

Egypt's opposition has been accusing Mr. Morsi and his Muslim Brotherhood movement of trying to undermine secular rights.

Activists are planning a massive anti-government rally in Cairo's Tahrir Square on Sunday, which is the anniversary of Mr. Morsi's ascent to the presidency last year.

Meanwhile, at least eight members of Egypt's upper house of parliament announced they were resigning, on Saturday, in protest of Mr. Morsi.